645973451 has 4 divisors (see below), whose sum is σ = 646268352. Its totient is φ = 645678552.

The previous prime is 645973399. The next prime is 645973459. The reversal of 645973451 is 154379546.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 645973451 - 2²² = 641779147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645973459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144140 + ... + 148553.

It is an arithmetic number, because the mean of its divisors is an integer number (161567088).

Almost surely, 2^645973451 is an apocalyptic number.

645973451 is a deficient number, since it is larger than the sum of its proper divisors (294901).

645973451 is a wasteful number, since it uses less digits than its factorization.

645973451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294900.

The product of its digits is 453600, while the sum is 44.

The square root of 645973451 is about 25416.0077706944. The cubic root of 645973451 is about 864.4467046442.

The spelling of 645973451 in words is "six hundred forty-five million, nine hundred seventy-three thousand, four hundred fifty-one".